The thriller Hush is more of a filmmaking exercise than anything else and, in this case, that’s not a bad thing. For much of the film’s lean running time, there are just two characters: a deaf woman living by herself in a home with no shades or curtains, and a murderous maniac just outside. He wants to kill her. She’s trying to figure out ways to survive. (Sort of an update to Wait Until Dark?) Director Mike Flanagan, who co-wrote the script with star Kate Siegel, creates a fairly gripping cat-and-mouse game that has a couple neat tricks and rarely relies on cheap thrills.

Flanagan acknowledges that Hush is a puzzle to be solved, a problem to be attacked, integrating the idea into the lead character of Maddie (Siegel). As an author, she has the uncanny ability to hear a voice in her head that can weave multiple endings to her stories, plotting outcomes with speed and accuracy. Even as we meet Maddie, she’s working out the potential of seven different endings for her latest book. You can imagine how useful that skill set could become when you’re trying to escape some unnamed madman.

The guy, played by the usually likable John Gallagher, Jr. (Short Term 12, The Newsroom) demands the most aggressive suspension of disbelief. Listed as “man” in the credits), he’s relentless enough to be scary, and careless enough to keep us guessing his rate of success, but there’s a problem: Gallagher plays him as a level-headed thinker without a lot of psychopathic gestures or discernible personality disorders. Makes it awfully hard for us to align his clear-minded demeanor with his violence. With this disconnect and lack of narrative background, Hush the exercise emerges, more of a chilling action-adventure without motives.

But the action is solid. Maddie spends an uncomfortable amount of time facing off with the man, literally, as he stands outside her kitchen door and they eye each other through the glass. As she moves from room to room – sometimes in fear, sometimes in strategic mode – Flanagan finds a way to build on the story, adding a weapon or an attempted escape, each new setting bringing something fresh to the film. The achievement is in the lack of repetition from point to point. (It makes sense that Flanagan has been named to direct the adaptation of Stephen King’s Gerald’s Game.)

When things do have the possibility of settling in, the script changes the point of view or makes a strong move to increase the tension – frankly, the idea of a murderer staring clearly at you through a window is tense enough, thanks. But Flanagan has worked out his visual playbook very well, the participants bobbing and weaving through the enclosed environment. It reminds me of the “bottle” episodes that occur on big-budget television shows – those standalone episodes that take place in a single setting with few characters, primarily to save a week’s worth of budget.

There are some plausibility issues regarding Maddie’s ability to sense certain things, and that plays an increasing role as Hush moves along. If there were some more authentic narrative backbone to why this was all happening, it might be more forgivable. But all we have is the puzzle and the pieces in it, so the authenticity needs to be there all the way in the action. And I just wasn’t sure that was the case.

Kudos to the two leads for some considerable commitment, Siegel especially. And applause to both her and Flanagan for not making Maddie a cowering wimp, but also making sure she wasn’t a pain-free superhero either.